Combination Sum

Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.

The same repeated number may be chosen from C unlimited number of times.

Note:

• All numbers (including target) will be positive integers.
• Elements in a combination (a1, a2, … , ak) must be in non-descending order. (ie, a1 ≤ a2 ≤ … ≤ ak).
• The solution set must not contain duplicate combinations.

For example, given candidate set 2,3,6,7 and target 7, 
A solution set is: 
[7] 
[2, 2, 3] 

class Solution {
public:
    vector<vector< int> > combinationSum(vector< int> &candidates,  int target) 
    {
         // sort candidates
         int size=candidates.size();
         for( int i= 0;i<size;i++)
             for( int j=i+ 1;j<size;j++)
                 if(candidates[i]>candidates[j])
                {
                     int tmp=candidates[i];
                    candidates[i]=candidates[j];
                    candidates[j]=tmp;
                }
         // dfs
        vector<vector< int>> result;
         if(size== 0)  return result;
        
         int v[target/candidates[ 0]];
         int cdep= 0;
         int vdep= 0;
        dfs(result,candidates,size,v,cdep,vdep,target);
         return result;
    }
    
     void dfs(vector<vector< int>>& result,vector< int> &candidates, int& csize, int* v, int& cdep, int& vdep, int& target)
    {
         if(target== 0)
        {
            vector< int> vals;
             for( int i= 0;i<vdep;i++)
                vals.push_back(v[i]);
            result.push_back(vals);
             return;
        }
         if(cdep==csize || target<candidates[cdep])  return;
        
         int dup=target/candidates[cdep];
         for( int i= 0;i<=dup;i++)
        {
             // add to v
             for( int j= 0;j<i;j++) v[vdep+j]=candidates[cdep];
             // search next candidate
            target=target-i*candidates[cdep];
            cdep=cdep+ 1;
            vdep=vdep+i;
            dfs(result,candidates,csize,v,cdep,vdep,target);
            vdep=vdep-i;
            cdep=cdep- 1;
            target=target+i*candidates[cdep];
        }
    }
};